This invention relates to a printing blanket which is self recovering after smashing thereof and to a method of making such a blanket.
Printing blankets comprised of a plurality of laminated layers are in wide use throughout industry and are often used in offset lithography where the usual function of such a blanket is to transfer printing ink from a printing plate to paper being printed. During the course of using such a printing blanket in offset lithography the blanket may be subjected to large compressive forces or smashing and such smashing is defined as a deformation of the blanket which causes a substantially permanent reduction in its thickness or gauge. The smashing of such a blanket results in an instant deterioration in the quality of the printing and this is due to the fact that the smashed area of the blanket will not transfer printing ink from the plate to the paper in a satisfactory manner.
The usual way of solving the problem of a smashed blanket is to remove such blanket and replace it with a new one. However, there are some instances where it can be determined by inspection that the blanket is not seriously damaged and it is possible to restore the smashed area by swelling layers adjoining the smashed area using a suitable solvent. With either of these solutions, it is necessary to stop the printing press and remove the damaged blanket and this results in substantial material losses but more importantly results in loss of valuable press time.
Printing blankets have been proposed heretofore where efforts have been made to make them sufficiently compressible that they are not damaged by moderate compressive forces. Further, printing blankets of laminated construction have been proposed that are smash resistant.
However, the desired optimum situation would be to provide a printing blanket and method of making such a blanket which when subjected to excessive compression or smashing is self-recovering, i.e., the construction of such a blanket is that it restores itself to its original thickness, without stopping and removing the damaged blanket or stopping the associated printing apparatus or press.